1 Technical Field
This disclosure relates generally to a starter working to start an internal combustion engine.
2 Background Art
Some starters for internal combustion engines are engineered to advance a pinion gear using a pusher to bring the pinion gear into engagement with a ring gear mounted on the engine and rotate the pinion gear using torque produced by an electrical motor to start the engine. Japanese Patent First Publication No. 2010-248920 teaches such a type of starter.
The above type of starter has a risk that the pinion gear is moved forward, but a tooth of the pinion gear fails to achieve engagement between teeth of the ring gear, in other words, after colliding with a side surface of the ring gear, the tooth of the pinion gear continues to be pushed against the side surface of the ring gear while being rotated and then achieves success in engagement between the teeth of the erring gear. The collision of the pinion gear with the ring gear will generate mechanical noise. In order to alleviate such noise, starters have been proposed which has a buffer, such as rubber, which is disposed between the pinion gear and the electric motor to absorb impact power or reactive force generated upon the collision of the pinion gear with the ring gear, thereby reducing the collision noise.
Japanese Patent First Publication No. 2006-161590 teaches a starter designed to have an elastic member, such as a spring, which is disposed between a pinion gear and an electric motor to assist in shifting the pinion gear to a ring gear mounted on an engine when the pinion gear has failed to engage the ring gear.
Pinion shift starters work to shift the pinion gear in an axial direction thereof about which the pinion gear rotates to achieve mesh with the ring gear. Usually, an end face of the pinion gear collides with that of the ring gear, after which the pinion gear is rotated to complete the mesh between the pinion gear and the ring gear. In order to ensure the stability in mesh between the pinion gear and the ring gear upon the collision thereof, use of an elastic member, like in the above latter publication, which is disposed on a rear end of the pinion gear has been proposed. When the end faces of the pinion gear and the ring gear collide with each other, the elastic member continues to push the pinion gear against the ring gear until completion of mesh between the pinion gear and the ring gear, thereby minimizing rebound of the pinion gear upon the collision to achieve success in engagement between the pinion gear and the ring gear. The elastic member is, thus, required to produce elastic pressure which advances or urges the pinion gear in an axial direction thereof until the completion of mesh of the pinion gear with the ring gear after the pinion gear collides with the ring gear. For instance, an initial load may be applied to the elastic member to produce a large elastic pressure and also achieve a long stroke of the elastic member. This, however, requires a degree of force which is greater than the initial load to compress the elastic member, thus resulting in a risk that mechanical noise occurs upon collision of the pinion gear with the ring gear.
A buffer, like in the starter taught in the above former publication, may, therefore, be used in addition to the elastic member to assist in shifting the pinion gear. The arrangement of the elastic member and the buffer, however, encounters the following drawbacks. The elastic member is, as described above, subjected to the initial load, so that an initial elastic pressure, as produced by the elastic member resulting from the application of the initial load thereto, acts on the buffer arranged adjacent the elastic member. This may cause the buffer to be undesirably compressed by the initial elastic pressure produced by the elastic member before the buffer undergoes reactive force from the ring gear, which may lead to a failure in operation of the buffer and generation of mechanical noise.